Pigment ink provides excellent light fastness and water fastness. Therefore, pigment ink is becoming more prevalent in inkjet technology for document and photo printing applications. Unlike dye-based inkjet inks, pigment inks contain particles. When the ink is printed on to the substrate, the resulting roughness of the ink surface tends to be much higher than the surface printed by dye-based inks. This high surface roughness leads to lower gloss.
It is difficult to achieve the same gloss value with pigment ink as with dye-based ink. There are many ways to improve the photo gloss of pigment inks. Reducing particle size is one way to achieve the higher photo gloss, but it has limitations. Some surface energy reducing agents could provide better wetting and fast diffusion. The surface roughness of the pigment is related to the formation of the pigment as filter cake, and the roughness characteristics influence the functions of the ink wetting and diffusion of ink ingredients into media.
The addition of certain surfactants and penetrants to pigment ink formulations is known to alter the wetting and diffusion, which reduces the surface roughness and achieves higher gloss of the printing image. Such materials lower the dynamic surface tension of the pigment ink.